I wouldn't say I've understood this to be a rule.. maybe he just had the same impression of you that you did of him and was moved to do something special for you out of gratitude? I've had many surfers bring beer, and generally travel with a bottle of wine to offer to share my host(s) if they're into drinking. Some hosts make it explicit in their profiles that they expect you to do something for them, tidy up, cook them something, etc. which I think is really against the originally intended spirit of couchsurfing. I'd say that the rules on couchsurfing are the same as rules in friendship. You and a good friend may help each other out time and time again with things like moving, dogsitting, and advice. There are no 'rules' about what you should do for your friend or vice versa, and personally I have the best experiences with people who match my level of engagement or generosity without me expecting or asking for it. There's way too much drama between people who feel like they're being used in a relationship, and I think that stems from people having too many expectations of others. What I'm getting at, is that many people may have expectations of couchsurfers, as with any other relationship in life. But the couchsurfing community's only explicit expectations are good communication, honesty, and respect. I think the point is that people who consider obligatory gifts to be part of the experience are conflating ideas they've gotten elsewhere with the ideals of couchsurfing.